Induction seaming tapes, systems and methods

ABSTRACT

The present invention pertains to novel tapes, tools and seaming systems for creating seams of rolled goods, especially carpeting, using induction heating. The present invention also provides improved seaming tapes for use in resistive heating methods.

This application is a divisional of application Ser. No. 10/449,209,filed May 30, 2003, now U.S. Pat. No. 6,921,886, and is based upon andclaims priority from U.S. Provisional Patent Application No. 60/384,523.Holzer et. al. filed May 30, 2002.

TECHNICAL FIELD

This invention relates to induction activated seaming tapes, inductionseaming systems and methods of seaming using induction for use inassociation with the formation of bonded seams of “rolled goods”including textiles, fabrics, felt, carpeting, wall coverings, and thelike as well as rigid and semi-rigid goods including paperboard, highpressure laminates, and the like.

BACKGROUND OF THE INVENTION

It is well known to attach rolled goods and other rigid and semi-rigidgoods to an underlying surface or substrate through any number oftraditional methods including mechanical fasteners such as nails,staples, screws, tacks and brads, and chemical fasteners such asadhesives and cements which cure by volatilization of solvents, heat orchemical reaction. Additionally, Remerowski et. al. (U.S. Pat. No.5,935369) and Krzeszowski (U.S. Pat. No. 4,123,305) teach methods ofbonding rolled goods to a work surface through induction bonding.However, in many applications, especially carpet seaming, it isundesirable to effect a bond between the rolled good and the underlyingsubstrate or intermediate, in the case of a carpet and the intermediatecarpet padding, while creating a seam bond between opposing edges of therolled good or of adjacent pieces of a rolled good. While stitching ofseams is common for most rolled goods applications involving fabrics andtextiles, stitching is not always practical or possible, especially inapplications where the presence of a visible seam would be unsightly ason a large tapestry, canvas or the like.

In order to address concerns relative to seaming of rolled goods withoutstitching, a number of different technologies and methods have beendevised. For example, simple heat activated tapes comprised of a backingand a layer of a hot melt adhesive on one or both sides of the backinghave been developed for butt end and overlap seaming, respectively, ofgenerally thinner fabrics and textiles or overlap seaming of thickerfabrics and textiles. These tapes are activated in place by passing atraditional consumer iron over the site of the seam.

The heat of the iron passes through the fabric or textile to theadhesive, melting the same and forming a bond once the heat source isremoved and the hot melt allowed to cool. However, care must be taken informing the seam so as to avoid scorching the fabric or even melting ofthe fabric (especially in the case of certain fabrics of low temperaturesynthetic polymers and elastomeric materials) with the hot iron as wellas leakage or squeeze-out of the adhesive from the edges of the tape.Furthermore, if adhesive leaks through the seam or bleeds through therolled good itself and comes in contact with the hot iron, noxious fumesmay arise and, more importantly, the iron may no longer be suitable forits traditional use of pressing or ironing articles of clothing and thelike.

The problems associated with the use of adhesive tapes are compoundedand magnified in the seaming, particularly butt end seaming, of heavyduty, thick fabrics as used for tapestries and curtains and especiallyin the seaming of carpets. For convenience, the following discussionwill be directed to carpet seaming. Carpet seaming tapes are generally3–6 inches in overall width and are comprised of a heat-activatedadhesive coated in the central 2–5 inches of these tapes, preferably ahot melt adhesive, a reinforcing fabric, and a carrier paper, oftentimescoated with a silicone release coating on the backside. A generalschematic of the traditional carpet seaming tape is shown in FIG. 1where the tape 1 includes a paper backing 2, often creped and frequentlycoated with silicone release coating on the reverse side 4, areinforcement strip or scrim 3 for strength and a thermally activatableadhesive 5. Reinforcement strip 3 can be a knit or woven material andmay extend to the edge of the tape but is frequently ½ to 1 inchnarrower than the paper carrier leaving equal spacing on each edge. Theadhesive may be in the form of a layer or beads or a combinationthereof, but, in any event, is placed a set distance from the edges ofthe tape to prevent the molten adhesive from flowing off the tape andinadvertently bonding the carpet to the pad during the heating andsubsequent pressing steps. If this should occur, the silicone releasecoating on the underside of the tape ensures that the tape itself willnot bond to the padding, although this will not prevent the back of thecarpet adjacent to the tape from bonding to the pad.

This seaming method requires the operator to first place the seamingtape, adhesive side up, directly under the open seam defined by theopposing edges of the carpeting. Once the carpet and tape are properlyaligned, the operator then lifts the carpet and inserts a specializedheating iron, whose lower surface is elevated to a sufficienttemperature to activate or melt the adhesive, underneath the carpet andin direct contact with the heat activated adhesive of the seaming tape.Once the underlying adhesive has been melted or reacted, the hot iron isadvanced along the seam to heat the next section of adhesive.Concurrently, the trailing edges of the carpet behind the iron arebrought in contact with the molten adhesive, manipulated to mateopposing edges of the carpeting to match any designs that may beincorporated into the carpet, and then pressed into the molten adhesiveto ensure good surface contact and integration of the molten adhesiveinto the rough surface of the carpet backing. Thereafter, the adhesiveis allowed to cool to form the bonded seam. The desired outcome is aseam that is not distinguishable from the rest of the carpet when viewedfrom the top of the carpet after the carpet has been stretched onto atack strip or like device that holds the finished carpet in place.

Though the foregoing is the most commonly practiced method of carpetseaming, it is not without its disadvantages. One particulardisadvantage is the incidence of peaking of the carpet at the seam oncethe carpet is stretched. Numerous improvements to the carpet seamingtapes have been proposed for addressing this problem including the useof multiple tapes in a side-by-side relationship (Johnston et. al. U.S.Pat. No. 4,749,433), extra-wide tapes (Johnston et. al. U.S. Pat. No.4,919,743), and plastic or metallic reinforcing elements (Matthews U.S.Pat. Nos. 5,691,051 and 6,110,565 and Matthews et. al. U.S. Pat. No.5,198,300). Others have proposed the use of an excess of adhesive at thecenterline of the tape. One way in which this has been achieved isthrough the use of specialized irons that include channels or channelingfeatures on their lower surface which divert molten adhesive so as tocreate a ridge of excess adhesive directly under the seam. While all ofthese provide some relief to the peaking problem, they do so at theexpense of added costs in relation to the materials and manufacturing ofthe tapes and/or tools.

While the modified irons would seem a most efficient means to ensureadditional adhesive at the seam, they are not without problems andshortcomings. Most notably, if the adhesive is heated significantlyabove its melting point, its viscosity becomes so low that a substantialamount may flow away from the ridge region as the tool is advanced andbefore the applicator can properly align and place the carpet edges.Additionally, because the adhesive in the formed ridge area is exposedto the air for the longest period of time, cooling will result in somesolidification or viscosity build up in the adhesive in this area sothat even if the applicator can ensure that adhesive is present at theinterface of the abutting edges, surface wetting may not be sufficientto ensure a strong bond at the interface, i.e., by the time theapplicator is able to align and place the carpet edges in properposition and press the same into the adhesive, the adhesive may not beviscous enough to flow into the interface between the abutting edgesand/or to develop a sufficiently strong bond with the consequence thatwhen the carpet is stretched the abutting edges separate or open: muchlike a paper cut opens when one pulls the skin on opposite sides of thecut in opposite directions.

In addition to the foregoing problems, the hot iron method does notallow for ease of redoing a seam once formed. Should the applicator findthe pattern is off or that a gap exists in the seam bond, he must employextreme care in reopening the seam to the point of the problem. In thismethod, the only way to open the seam is to rip it apart and then stripthe tape from the back of the carpet. This process can severely damagethe carpet and the carpet backing. Similarly, this method and tool donot allow for simple repairs in the event one needs to replace a smallsection of carpeting, for example to repair a cigarette burn, or tore-bond a small segment of the seam that has opened due to traffic. Inessence, one must open an area sufficiently large to enable the tool tobe placed under the carpet and removed. Furthermore, the heat of thetool often causes a relaxation of the twist of the carpet pile resultingin a noticeable difference in the carpet texture at the seam.

Besides the aforementioned difficulties with the process, the hot ironmethod has a number of additional concerns as well, including health andsafety related concerns. For example, the hot iron generates theemission of strong, offensive fumes from the adhesive. Additionally,because the irons, during use, generate a build up of adhesive andadhesive residue on the underside of the iron, i.e., that side incontact with the adhesive, the operator must often raise the temperatureof the tool periodically during the seam forming operation in order toensure good melting/activation of the adhesive. This can even occurduring a single seam forming operation where it is not possible tointerrupt a seaming operation to remove and clean a tool withoutseriously risking problems. As noted above, such higher temperaturesresult in lower viscosities of the adhesives, increasing the likelihoodthat adhesive will leak beyond the tape edges and bond the carpet and/orthe tape to the underlying pad or flooring as well as through the tapebacking itself. Additionally, such hot irons can permanently distort thecarpet backing as well as the carpet structure itself as a result ofscorching or, in the case of polymer based materials, melting and/orrelaxation of the carpet fiber twist; cause severe burns in workers whoaccidentally touch or come in contact with the hot surface of the iron;cause the emission of noxious fumes as a result of the melting andscorching of the adhesive. Additionally, a build up of adhesive andadhesive residue on the iron interferes with the heat transfer from theiron to the adhesive, thus slowing down the overall seaming process andunduly extending the time needed to complete the job.

A number of alternative technologies have been developed in an effort toaddress some of the problems with the traditional irons and seamingtechniques. In particular, concerns relative to adhesive buildup on theiron and the concomitant need for higher temperatures for the iron, andthe associated problems with such higher temperatures, are eliminated byseaming methods and devices wherein the heat needed for activating ormelting the adhesive is generated within the seaming tape itself and notools come in direct contact with the adhesive. Additionally, thesealternative methods involve tools that do not become excessively hot inuse and, thus, concerns for burns to the applicator or the carpet arenot an issue. Further these alternative technologies do not involve theuse of tools which travel beneath the carpet and above the seam tape,thus making the seaming method much easier.

One of the alternative methods involves resistance heating as a means ofmelting or activating the adhesive. For example, Brooks (U.S. Pat. No.4,416,713), Middleton (GB 1,499,801) and Rodenbaugh (GB 1,507,851) eachteach methods of carpet seaming using electrically conductive seamingtapes, i.e., seaming tapes similar to those used in traditional ironseaming methods except that they have an electrically conductiveresistance element incorporated into the tape. In practice, each end ofthe tape is connected to an electrical current supply source to create acircuit. Heat generated by resistance heating as the current passesthrough the conductive element then melts or activates the adhesive.This eliminates many of the problems with the hot iron method and devicebut creates additional problems as mentioned below.

Because the tape is activated for the whole length of the seam at once,special care must be taken to ensure that the whole seam is properlyaligned before inducing the current. Any movement of the carpet beforethe seam is cured or set, even as a result of a misstep by theapplicator at or near the seam, may throw the entire seam out ofalignment. Additionally, any break in the conductive element in the tapewill render the entire length of the conductive seaming tapeineffective. In this respect tears or breaks in the conductive materialmay occur during the manufacture of the tape, in the course of layingthe tape and carpet or as a result of forces pressing down on the tapeafter its placement, e.g., as a result of a misstep or the placement ofa heavy and/or sharp edged article on the seam. More importantly, thismethod requires costly, bulky and inconvenient current supply equipmentcapable of generating currents of over 100 amps in order to generatesufficient heat along a lengthy seam to sufficiently heat the adhesive.

To some extent the need for bulky and costly equipment may be addressedby superimposing one strip of the conductive material over another withan intervening electrically insulating material, isolating the one fromthe other, (Brooks U.S. Pat. No. 4,610,906) or by placing two narrowstrips of conductive material in a spaced, side-by-side relationshipalong the length of the seaming tape (Baxter AU57288/80). In use, aconductive bridge is applied linking each conductive strip to the otherat one end of the tape and the leads from the power source are attachedto the conductive strips at the opposing end of the tape. Both tapespresent problems of manufacture and handling to ensure that theconductive strips do not touch each other. In the latter, the stripsmust be placed carefully to ensure they do not touch; whereas in theformer, care must be taken to ensure that nothing pierces the tape, ahappenstance that could create a short through the electricallyinsulating layer. Furthermore, because the heat generated by theconductive material is fairly constant along the conductive element andacross its width (assuming uniformity in the material), the use ofthicker regions of adhesive can create problems as the time to melt theadhesive in such regions is longer than in thinner regions. Thus, theadhesive in the thinner regions will achieve a lower viscosity and havea greater tendency to flow before the adhesive in the thicker regions issufficiently melted to effectively bond the carpet. This can lead toleakage of the adhesive from the seam.

A second alternative carpet seaming technology relies upon inductionheating and induction activatable seaming tapes. Induction activatableseaming tapes are similar, in many respects, to the resistance tapesexcept that heating results from eddy currents and hysteresis effectsthat are induced in a susceptor material, e.g., a foil layer or strip,upon being exposed to electromagnetic fields. Although Middleton (GB1,499,801) primarily focused on resistance tapes wherein the conductivemedium is a perforated conductive foil, Middleton also indicates thatthese tapes may be activated by induction. Nakano (EP 0237657) alsoteaches carpet seaming using induction activatable adhesive tapes thatare activatable upon exposure to alternating magnetic fields of highfrequency. Finally, Sakai et. al. (JP 1200937 and JP1203825) teachinduction heating apparatus and induction carpet bonding methods whereinthe induction tool for generating the high frequency magnetic field hasthree circular coils in a linear relationship corresponding, in use, tothe centerline of the seaming tape. It is believed that this technologywas commercialized by Hiroshima in Japan; however, it has since beenremoved from the market due to poor performance and acceptance of theproduct.

While induction seaming methods as taught in the prior art will addressmany of the issues and detriments of the iron seaming method and theresistance seaming method, they still have various shortcoming of theirown. For example, leakage of activated or melted adhesive from the edgeof the tape is still of concern, especially if the adhesive as appliedto the tape is close to the edge. More importantly, induction tools andinduction activatable tapes taught to date for use in carpet seamingsuffer from poor heating in the area of the seam line or centerline.With such tapes and tools, the prominent heating occurs at the edge ofthe susceptor and not at the centerline of the susceptor. Indeed, thetraditional induction tools taught in the aforementioned art providelittle, if any, heating at the centerline of the tape due to the factthat the induced electric field and heating is very weak directly underthe center of the coil. Since the carpet seam itself overlies thecenterline of the tape, that area of the seam that most needs heat toensure a good bond receives the least amount of heat. Consequently,there can be un-bonded gaps or weaknesses in the seam as a result ofincomplete or insufficient heating of the adhesive directly under theseam. Although activation of the induction tool for longer periods oftime may allow additional heat to traverse the tape to the centerline,in reality this is not likely to occur to any significant extent sincethe more ready direction of heat transfer is through the foil to theother layers of the tape and carpet rather than across the thin foil.Consequently, even if such transverse heating were possible, by the timesufficient heat transferred to the centerline area, the other componentsof the tape and carpeting in contact with those regions of the tapewhere heating was effected, particularly at or near the edges of thesusceptor, would suffer from excessive heating resulting in scorchingand burning of the adhesive, other tape components and/or the carpeting.These problems are even further magnified and compounded if the tapesemployed thicker adhesive regions in the centerline area.

Thus, there remains a need in the art to design heat activatable tapesthat lessen or eliminate the concern for adhesive leakage orsqueeze-out, without increasing, or substantially increasing, the costsof the tape.

There also remains a need in the art to design tapes which are readilyactivatable by induction and provide suitable, durable carpet seams and,in a preferred respect, have thick regions of adhesive in the centerlineto enhance butt end bonding and reduce the likelihood of peaking withoutbeing concerned that excessive induction times and heat would be neededand without risking scorching or burning of the tape, the carpet backingor even the carpeting itself.

There also remains a need in the art to design induction seaming systemswhereby induction tools and tapes are specifically designed for use incombination so as to provide enhanced performance, whether foraddressing adhesive leakage or squeeze-out, peaking or merely forimproving bonding in the centerline region of the tape withoutoverheating the edges of the tape.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides novel seaming tapes, whichmay be activated by induction or resistance heating, wherein theincidence of adhesive leak or squeeze-out is greatly reduced if noteliminated. Such seaming tapes include isolated strips of a heat sinkmaterial, which may be of the same material as the conductive orsusceptor material, which run parallel to each edge of the tape andintermediate the edge of the tape and the susceptor or conductivematerial which tends to be centered on the tape. Although the strips ofthe heat sink material may be placed so as to leave a narrow borderalong the edge of the tape, much as current tapes leave a border tocatch squeeze-out adhesive, it is also contemplated that the outer edgesof the strips of heat sink material may be coterminous with the edges ofthe tape. This process results in the relocation of the traditionallyhottest part of the induction tape from the edge to a more inwardposition.

The present invention also pertains to improved seaming methods wherebyadhesive leakage or squeeze-out is significantly reduced or eliminatedas a result of the use of the foregoing seaming tapes as well as tocarpet seaming systems comprising the aforementioned seaming tapes andinduction tools designed to operate with said tapes.

In another aspect, the present invention provides novel inductionactivatable seaming tapes wherein the susceptor layer comprises twoelectrically isolated, parallel, co-planar susceptor elements that areseparated by a gap that essentially, and preferably, corresponds to thecenterline of the tape. In a preferred embodiment, the center region ofthe tape, including the aforementioned gap, is overlaid with a thickerbead or layer of adhesive, as compared to the average thickness of theadhesive across the width of the tape, so as to provide added adhesiveto ensure good bonding of the butt ends of the carpet at the seam.

The present invention also pertains to improved seaming methods wherebygaps or weaknesses in the seam bond due to incomplete or insufficientheating of the adhesive directly underlying the seam is eliminated as aresult of the use of the foregoing seaming tapes as well as to carpetseaming systems comprising the aforementioned seaming tapes andinduction tools designed to operate with said tapes.

In another, yet related aspect of the present invention, there areprovided improved conventional induction activatable seaming tapes,without the novel gap mentioned above, wherein the improvement pertainsto the inclusion of regions of thicker adhesive in the centerline areaof the seaming tape and improved induction tools specially designed foruse with such tapes. In following, the present invention pertains to animproved method of carpet seaming using the improved tapes to reduce oreliminate peaking and a double racetrack coil induction tool wherein thecoils are side by side, relative to the centerline of the tape and thecorresponding axis of the induction tool coil, as compared to prior artmulti-coiled tools where the coils are arranged in a linear or in-linerelationship relative to the centerline of the tape and the axis of theinduction tool.

Finally, in another aspect of the present invention, there are providedseaming tapes having the combined attributes of the above-mentioned tapedesigns as well as improved methods of seaming using such tapes as wellas the seaming systems comprising such tapes and the inductions toolsspecialized to optimize the performance of those tapes.

The use of these inventions results in improved seam quality withoutdrastically altering the seaming process and, in some instances,reducing costs. Additionally, the seaming methods of the presentinvention do not produce a significant amount of heat in, on or belowthe carpet, particularly as compared to the traditional seaming ironmethod; have reduced odorous emissions overall; and allow for easybonding from the top of the carpet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic representation of a conventional carpet seamingtape used with a seaming iron.

FIG. 2 is a cross-sectional view of the base and electrically activelayers of a seaming tape made in accordance with the present inventionwherein dead zones are present at the edge of the tape.

FIG. 2 a is a top view of the tape foundation of FIG. 2.

FIG. 3 is cross-sectional view of a completed seaming tape using thetape foundation of FIG. 2.

FIG. 4 is a depiction of the footprint of a double racetrack coil.

FIG. 5 is a cross-sectional view of the base and susceptor layer of aseaming tape made in accordance with the present invention wherein a gapor slit exists down the centerline of the susceptor layer.

FIG. 5 a is a top view of the tape foundation of FIG. 5.

FIG. 6 is a cross-sectional view of a completed seaming tape using thetape foundation of FIG. 5.

FIG. 7 is a graph showing the normalized power density across one-halfof the width of the susceptor (from the centerline to the edge) for fourdifferent coil separations.

FIG. 8 is a graph showing a finite element analysis of the normalizedpower density across one-half of the width of the susceptor (from thecenterline to the edge) for three different susceptor widths.

DETAILED DESCRIPTION OF THE INVENTION

In the simplest of terms, the seaming tapes made in accordance with thepresent invention comprise three key elements, a base layer, one or moresusceptor or conductive layers and one or more adhesive layers. Forapplications needing high strength, particularly transverse strengthacross the seam, the tape will also include one or more reinforcinglayers. It is possible, of course that the reinforcement may itself beintegrated into or comprise the base layer. While these very elementsform the structure of conventional induction and resistance seamingtapes, the tapes of the present invention differ markedly in terms ofthe design and construction of the susceptor or conductive layer and,insofar as they pertain to tapes suitable for induction activation, thedesign or configuration of the adhesive layer(s). The tapes according tothe present invention may be one-sided or if used to prepare anoverlapping seam or to bond a butt end seam to a substrate,double-sided.

Generally speaking, the tapes have a length and width which characterizethe plane of the tape. The height or thickness of the tape is determinedby the number of layers making up the tape as well as the thickness ofeach layer. The overall length of the tape is irrelevant since,typically, tape portions are cut from a spool of tape to fit thespecific application. The width of the tape is largely dependent uponthe application to which the tape is to be used. For example, forseaming light fabrics, it may be sufficient to employ a tape of about ½inch width or larger. On the other hand, tapes for heavy-dutyapplications, e.g., carpet seaming, will be on the order of three to sixinches or more. Generally, such tapes would not exceed eight or soinches as the costs associated with such widths make them prohibitivelyexpensive, not to mention the costs of constructing induction toolslarge enough to activate the tapes. Finally, the tape should be as thinas possible so as to avoid noticeable rises in the fabric, textile orcarpeting where the seam is formed as well as to retain flexibility inthe tape, especially so that it can be easily inserted into a cut in acarpet for easy repair and to enable sale in coiled form. The tapecenterline, as that term is used herein, is the midpoint of the tapeacross its width. In a seaming operation, the seam to be formed willgenerally line up directly above the centerline of the tape. In thisway, the surface area of the adhesive of the tape is equally apportionedto each end of the fabric, textile or carpeting to be bonded so as toachieve maximum strength and durability in the seam.

As noted above, the seaming tapes are built upon a base layer. Mostcommonly, this base layer is made of a paper, preferably flat, creped orextensible Kraft paper, or could be formed of any other materials, suchas cloth, plastic film, or the like, which currently is used for manyseaming tape constructions. The base layer itself may be of a laminateconstruction comprising multiple layers of the paper or the like as wellas incorporating a reinforcing material, e.g., individual fibers(continuous or chopped), a woven or non-woven fabric or mesh, a screenor other mesh like material, made of natural or synthetic materialsincluding fiberglass, nylon or polyester. The base layer is preferablyflexible so as to maintain ease of use and to allow the tape to becoiled.

The adhesive is typically a hot melt adhesive or a reactive hot meltadhesive. Such hot melt adhesives are generally solvent-free adhesivesbased upon a number of different chemistries including: ethylene vinylacetate (EVA) copolymers, styrene-isoprene-styrene (SIS) copolymers,styrene-butadiene-styrene (SBS) copolymers; ethylene ethyl acrylatecopolymers (EEA); and thermoplastic and reactive polyurethanes.Different hot melt adhesives have different ranges of temperature overwhich they are activated; however, many are characteristically solid attemperatures below 180 degrees Fahrenheit (° F.) and low viscosityfluids above 180° F. that rapidly set upon cooling. Others havetransition temperatures as low as about 150° F.: of course the actualtransition temperature of a given hot melt adhesive depends upon thechemistry of that particular adhesive.

Generally speaking, the temperature activation range of a given hot meltadhesive depends upon the ability of the adhesive to wet and flow ontothe surface of the adherends under the pressure and temperatureconditions of application. This is dependant upon the rheology of theadhesive, which is a function of the chemical composition and molecularweight of its constituents. By selecting and evaluating adhesives thatprovide end-use performance as required by the application as well asthose that have a broad activation range, one can optimize the tapedesign to achieve the maximum bond area and performance ensuring thegreatest factor of safety when used.

Essentially any hot melt adhesive used or known for use in carpetseaming applications can be used in the present invention. Such are wellknown and widely available. The adhesive is present as a continuouslayer of even or varying thickness across the width of the susceptor, asa series of parallel beads and/or strips extending the length of thetape or as a combination of the two. Alternatively, the adhesive may bepresent as beads, films or adhesive strips in the centerline region ofthe tape, preferably the centerline and the susceptor edge region of thetape. In the induction activatable tapes, where the adhesive is notpresent in the susceptor edge region, it is important that the width ofthe susceptor be significantly wider, generally at least about 1.3times, preferably about 2 times, wider than the width of the coil toavoid excessive heating at the edge of the susceptor.

As noted, the adhesive may be of uniform or, preferably, varyingthickness, with a greater thickness being present in the centerlineregion. Adhesive profiles (i.e. cross-sectional views) of varyingthickness may be achieved by any number of methods, as known to thoseskilled in the art, including extruding a film or strip of adhesive ofthe desired profile, by building successive layers of the adhesive atspecific locations on a base layer of adhesive or by laying a film ofliquid adhesive and using one or more scraper tools having the desiredprofile on its lower edge. The specific thickness of the adhesive layerwill depend upon the intended end use application. Thin films, generallyfrom about 1 to 3 mils may be used for simple bonding of textiles andfabrics; whereas thicker adhesive layers, generally on the order ofabout 10 to 200 mils, preferably 20 to 140 mils, more preferably 40 to100 mils, will be needed for heavy duty fabrics, especially carpeting.As noted herein, thicker regions of adhesive may be desirable forcertain end-use applications. In the latter, it is desirable to ensurethe adhesive is of sufficient thickness so that it will penetrate intothe rough underside of the carpet backing and, most preferably, into thecarpet seam itself to enhance bonding of the butt ends of the carpeting.

Conductive materials and susceptors suitable for use in the constructionof conductive tapes and induction activatable tapes, respectively, arewell known. Indeed, for the most part, suitable susceptors, as describedbelow, are also suitable for use as the conductive material forresistance heating applications, and vice-versa. Clearly there are,however, some instances where the two classes do not overlap. Forexample, extremely thin foils used for induction may not be able tocarry the current without burning through the foil in resistanceapplication. The latter may require thicker foils. Similarly, a seriesof parallel wires or conductive strips of very small width will performwell for resistive applications but will not have sufficient surfacearea to couple to the coil to enable induction heating. For ease ofreference, the two are oftentimes herein referenced aselectro-responsive materials.

The width of the electro-responsive material is a matter of the width ofthe bond line to be formed as well as the method by which it is to beactivated. For resistive heating and conductive elements, the widthand/or number of conductive elements are gauged by the width of the bondline. On the other hand, for induction applications, the width of thesusceptor element or elements must be sufficient that theelectromagnetic field generated by the coil of the induction tool usedwill create eddy currents in the susceptor and that the eddy currentsgenerate sufficient heat, but not excessive heat, to melt the adhesiveto form a suitable bond. If the width of the susceptor is too small,there is insufficient width for the eddy currents to form. Even whereeddy currents are generated, the width must be sufficiently large toavoid excessive heating at the edges. Thus, proper susceptor width is amatter of coil design and size as well as the width of the bond area tobe formed.

Electro-responsive materials suitable for use in the construction of thelaminates of the present invention include essentially any structuralmaterial capable of absorbing electromagnetic energy and converting suchenergy to heat. For example, the electro-responsive material may becomprised of a carbon fabric, mesh screen or a metal or metallizedmaterial selected from foils, sheets, fabrics and meshes or screens. Thefoil or sheet may be continuous or solid across its surface or it mayhave random or patterned slits, punch-outs or cutouts. Metals useful inthe preparation of the electro-responsive materials include copper,steel, aluminum and other electrically conductive metals. Generallyspeaking, the electro-responsive material or electro-responsive layerhas a thickness of about 0.01–3 mils (0.00001 inch–0.003 inch) or more,preferably 0.05–2 mils, or most preferably 0.01–1 mils. In the case ofeddy current induction, especially when aluminum foil is used, thethickness of the susceptor layer may be somewhat less, from 0.01–2 mils,preferably 0.05–0.75 mils, and most preferably 0.08–0.55 mils. Thespecific selection of the susceptor material and form of the susceptormaterial is dependent, in part, upon the type of electromagnetic energyto which the tape is exposed, e.g., low frequency, medium frequency, andhigh frequency. For convenience, practicality, and safety, heating ispreferably developed using low to medium frequency electromagnetic waves(˜2 kHz to ˜1 MHz) by induced eddy currents alone or in combination withhysteresis heating. In this respect, it is preferred that the susceptorbe in the form of a sheet, foil, or mesh, which may be perforated,non-perforated, or patterned, with or without a constant thickness, andmade of aluminum.

Additionally, the seaming tapes of the present invention may include areinforcing layer comprising individual fibers (continuous or chopped),a woven or non-woven fabric, webbing or mesh, or other webbing, mesh orscreen like material, made of natural or synthetic materials includingfiberglass, nylon or polyester. This reinforcing layer is sewn or bondedinto the tape construction to provide lateral strength across the seam.

While many of the materials from which the tapes of the presentinvention are conventional for conductive and induction activatableseaming tapes, it is the novel orientation and configuration of theseelements as taught by the present invention which provide unique andmarkedly improved seaming tapes, and resultant seams, overcoming many ofthe short falls of the state of the art resistance and induction seamingtapes. For convenience, the following discussion will be specific tocarpet seaming tapes, methods and systems; however, those skilled in theart will readily be able to modify the teachings and principles setforth herein to use the same for seaming most any kind of “rolledgoods”, including textiles, fabrics, felt, carpeting, wall coverings,and the like, as well as rigid and semi-rigid goods includingpaperboard, high pressure laminates, and the like. It is understood thatthe term “rolled goods” is used herein to refer to a general category ofgoods and is not to be literally construed. While most roll goods aresold in bulk in a roll form, the present invention clearly applies togoods of the type described that are in sheet form as well.

Carpet seaming requires the creation of a band of bond area along theseam line of two pieces of carpet that are being joined. The bond mustbe essentially continuous along the length of the seam and must besomewhere between about ½ inch and about 4 inches wide. Additional bondareas may be present, for example, there may be a separate bond linealong or near the edge of the tape; however, the key bond area is thebond in the centerline area of the tape. Gaps or weak spots in the bond,of significant size, will open up when the seam is stretched and beunsightly in the finished seam as well as result in a seam of poor orlow durability. The preferred centerline bond width is between about 1inch and about 3 inches, most preferably about 2 inches in width. Thiswidth provides a good trade between strength (wider is stronger and moredurable under foot traffic) and cost (wider uses more adhesive and istherefore more expensive).

According to a first embodiment of the present invention, seaming tapesthat exhibit a markedly lessened tendency to experience edge leak orsqueeze-out of adhesive or that are free of edge leak or squeeze-out canbe produced by creating “dead” zones in the susceptor material orintroducing a co-planar strip of a damming material between thesusceptor material and the edge of the tape, preferably along the edgeof the tape. As shown in FIGS. 2 and 2 a, the foundation 10 of a seamingtape according to this embodiment of the present invention comprises abase layer 11, generally a strip of Kraft paper, and a susceptor layer12. The susceptor layer 12 comprises the susceptor element 14 andisolated edge strips 13 isolated by slits 17. The edge strips may be ofthe same material as the susceptor element or a different material solong as they do not generate or conduct sufficient heat to melt theadhesive when placed in the electromagnetic field. However, it is notedthat the material comprising the dam or edge strips, as they areinterchangeably referred to in this application, may, in fact, be a heatsink material, i.e., a material that readily absorbs heat from othermaterials in which it is in contact, so long as it does not conductenough heat to enable or facilitate the flow of adhesive past the dam tothe edge of the tape. Suitable damming materials include hightemperature polymers and plastics, preferably elastomeric or flexible innature, paper or paper-like materials, as well as metal foils,regardless of whether the metal is electrically conducting ornon-conducting. As shown in FIG. 3, the seaming tape is completed by thesubsequent addition of one or more adhesive layers 15 and, optionally, areinforcing layer 16, which may be directly adhered to the susceptorlayer or applied to an intervening adhesive layer 15 a. The uppermost ortop layer of the construction is an adhesive layer.

The width of the edge strips is generally less than ½ inch, preferablyless than ¼ inch. In any event, the width of the edge strip 13 is suchthat eddy currents and/or hysteresis heating cannot be achieved in theedge strip sufficient to melt the adhesive when an induction tool,otherwise capable of activating the seaming tape, is centered over theseaming tape and activated. This is generally seen when the width of theedge strips are about ¼ or less the width of the coil of the inductiontool.

The seaming tapes of this embodiment may be constructed in differentways. The simplest and most cost effective manner involves theapplication of the susceptor material over the whole of the surface ofthe base layer followed by a scoring of the susceptor layer so as toelectrically isolate the scored edge strips 13 from the rest of thesusceptor 14. Alternatively, the susceptor layer 12 comprises asusceptor element and two edge strips 13 of a damming material that areindependently laid on the base layer 11, preferably with a gap betweenthe edge strips and the susceptor element. Depending upon the selectionof the material from which the base layer is made, it may be necessaryto apply an adhesive to the underside of the susceptor material and/ordamming material in order to ensure a strong bond. Additionally,although not necessary, in constructing the tape according to thisembodiment, the base layer may be wider than the susceptor layer so asto leave an edge, much like traditional seaming tapes. However, thisadds costs and increased difficulty in manufacture due to the use ofmore material, i.e., a wider base tape, and the need for precision inensuring that the susceptor layer elements are properly centered on thetape. Such precision may be difficult in high-speed continuousmanufacturing operations.

The foregoing discussion just as readily applies to the manufacture andconstruction of those tapes that are activated by resistance heating aswell: the only difference being to ensure that the electro-responsivematerial is a suitable conductor for the specific application. As withthe induction tapes, the key is to isolate a narrow region along eachedge that is not electrically activated. As with the susceptor, it maybe a matter of scoring (cutting) the edge of a wide conductive foil orthe laying of independent damming materials. If a series of inductiveelements were laid side-by-side along the length of the tape, one couldachieve the “dead zone” effect merely by not attaching the current leadto those conductive elements near the edges of the tape.

The foregoing tapes may be activated by resistance heating, wherein alead is attached to each end of the tape or, where the tape has two ormore conductive elements with a conductive bridge at one end, to eachconductive element at the other end and a current passed through theconductive element to heat the adhesive, or by induction. In the latter,essentially any type of induction tool may be used to induce activationof the adhesive. Suitable induction tools are described in, for example,Riess et. al. U.S. Pat No. 6,509,555 and Sakai et. al. JP 1200937.Alternatively, and preferably, the tapes according to this embodimentare induced using induction tools having a “double racetrack” coil, i.e,two induction coils, preferably elliptical in shape and of the pancakestyle, in a side-by-side, substantially co-planar relationship, eachcoil, in operation, on opposing sides of the centerline of the seamingtape. FIG. 4 shows the footprint of a double racetrack induction coil 20having two elliptical coil elements 21 with opposite current flows 29separated by gap 22 on opposing sides of the central axis 23 of thetool. The functional length 25 of the coil 21 corresponds to that lengthof susceptor able to be heated to the appropriate temperature by thecoil. As discussed further below, the double racetrack coil not onlyprovides excellent heating at the edges of the susceptor element, butalso provides marked heating at the centerline of the tape.

Regardless of what tool is chosen, the seam is formed by centering theimproved carpet seaming tape below the carpet seam, placing the opposingedges of the carpet in butt end relationship with the seam overlying thecenterline of the underlying seaming tape, placing the induction toolover the seam with the central axis of the tool generally overlying theseam, and, thus, the centerline of the tape, activating the tool for asufficient period of time in order to melt the adhesive on the tape,moving the induction tool forward a distance equal to or less than thefunctional length of the induction coil to heat the next contiguoussection of tape while concurrently pressing the trailing carpet edgesinto the molten adhesive. Leakage or squeeze out of adhesive isprevented as a result of the “dead” zones. Specifically, in thoseseaming tape constructions where the adhesive overlies the edge strips,any heat generated in the edge strips and/or conducted through theadhesive from the susceptor element is insufficient to melt theadhesive. Thus, the adhesive overlying the edge strip acts as-a dam.Where the adhesive does not overlie the dead zone or only in a minorway, molten adhesive over the susceptor element may flow towards theedges but is quickly cooled and its flow stopped as the heat from themolten adhesive is absorbed by the heat sink.

In addition, this concept allows for the mass production of seamingtapes wherein the foundation of the seaming tape is first produced inwide stock rolls. These stock rolls are then cut to the desired width ofthe final tape and scored to create the appropriate “dead” zones. Forexample, a single stock roll of the tape foundation could be formed thatis several feet wide and is subsequently cut into individual 3 inch or 4inch wide tapes. In manufacturing the stock rolls, each layer ofmaterial making up the tape foundation is sequentially laid, one uponthe other, across the full width of the stock roll. Thereafter, theremaining layers of the tape are sequentially added to cut stock rollsto form the final tape construction. Alternatively, if the stock roll isto be used to manufacture a single width tape, it is possible tocomplete the build-up of the final tape, before cutting the rolls fromthe foundation tape, by scoring the bulk roll of the tape foundation andthereafter continuing with the build-up. In this embodiment, each layer,including the adhesive, would run from one edge of the tape to theother. Without the “dead” zones, these tapes would readily ooze adhesivefrom the edge of the tape. Thus, tapes according to this aspect of theinvention provide a number of manufacturing and materials related costefficiencies as well as addressing the problems of adhesive leakage andsqueeze-out.

In a second aspect of the present invention the susceptor element orlayer is scored (cut through) along its central axis, not to preventmelting of the adhesive, but to enhance melting of adhesive in the areaproximate to the scoring. FIG. 5 shows a cross section of the foundation30 of a seaming tape made in accordance with this embodiment of thepresent invention wherein a susceptor layer 33 is centrally disposed ona base layer 32 whose width is greater than that of the susceptor layer,leaving exposed edges 35 of the base layer to catch any leakage orsqueeze out of adhesive. Alternatively, the width of the base layer andthe susceptor layer may be the same, especially if the overall width ofthe susceptor is significantly larger than that of the coil. Critical tothis embodiment is the scoring of the susceptor layer along itscenterline, forming slit 34 along the length of the tape. The scoringisolates each portion of the severed susceptor element from the other.As shown in FIG. 6, the seaming tape is completed by the subsequentaddition of one or more adhesive layers 36 and, optionally, areinforcing layer 37, which may be directly adhered to the susceptorlayer or applied to an intervening adhesive layer 36 a. The top oruppermost layer of the construction is an adhesive layer. Alternatively,rather than applying a single susceptor layer and scoring it, one canachieve the same effect by placing two strips of susceptor element in aparallel, co-planar relationship, separated by a minor gap, sufficientjust to electrically isolate one from the other.

In a preferred embodiment of this aspect of the invention, the adhesiveon the uppermost surface of the seaming tape will be thicker in thatregion overlaying the centerline of the tape, essentially correspondingto the desired seam bond or bond width. Generally, the width of thisregion of thicker adhesive overlying the centerline of the tape will beabout 3 inches or less, but preferably no less than about ¼ inch inwidth. However, narrower regions of 2 inches or less, but preferably noless than ½ inch, are more common. The thickness of the adhesive in thisregion will be from about 40 to 200 mils, preferably from about 50 to150 mils. This will generally correspond to a thickness of one andone-half to five, preferably two to three, times the average thicknessof the adhesive across the width of the tape in those tapes whereadhesive covers all or substantially all of the susceptor surface area.Whatever the exact thickness may be, the purpose of this central ridgeor strip of adhesive is to provide excess adhesive that flows into theseam providing a strong bond between the opposing butt ends of thecarpet so as to avoid peaking when the carpet is stretched. Oftentimes,with thin films of adhesive over the whole of the tape or, especially inthe central region, there is insufficient adhesive to flow into the seamand bond the butt ends together. Consequently, when the carpeting isstretched, the seam, or at least the upper portion of the seam may open,causing peaking of the carpet seam. The excess or thicker regions ofadhesive are not necessarily limited to the central area of the tape.Such thicker regions may also be employed at the outer edges of thesusceptor elements as well as in the central region to provide betteroverall bond strength across the whole of the seam area, including boththe centerline bond area and the edge region.

It is also contemplated that this embodiment of the invention mayintegrate the “dead” zone concept of the prior embodiment. In thisrespect, the susceptor layer may be formed by scoring a susceptorelement three times: once at the centerline and once at the appropriatedistance in from each outer edge of the tape so as to form the edgestrips, as taught previously. Alternatively, the tape may be made bylaying each edge strip and each susceptor element strip independently orby scoring the centerline of the susceptor element and laying the edgestrips independently. Furthermore, where the tape construction employssuch “dead” zones, it is not necessary to use a base layer that is widerthan the susceptor layer to prevent adhesive from leaking out andbonding the carpet to the underlying substrate.

This aspect of the invention is especially beneficial as it enables theapplicator to use traditional induction tools having a single coil ormultiple, in-line coils, of the type described in Reiss et. al. andSakai et. al., respectively. Suitable coils may be of different shapes,e.g., square, round, oval, elliptical; but in any event must be properlysized so that they produce a heating pattern that is within the desiredbond band. Coils of large diameter or width in comparison to the widthof the susceptor element in the tapes will result in excessive heatingat the edge of the susceptor and, possibly, subsequent scorching and/ordegradation of the adhesive, tape, carpet and/or pad. Generallyspeaking, the width or diameter of the coil will be such that the widthof the susceptor will be from about 1.0 to 1.5 times the width of thecoil, preferably from greater than 1 to 1.3 times the width of the coiland most preferably about 1.1 to 1.2 times the width of the coil. Here,the width of the susceptor is the combined width of theindividual/scored susceptor elements.

This aspect of the present invention allows the construction of seamswithout concerns that gaps or weak areas in the bond at the seam willappear, particularly where one employs an excess of adhesive in thecenterline region. Specifically, the present invention allows for theuse of tools that previously provided little or barely sufficient heatat the centerline of conventional, non-scored induction tapes or didproduce sufficient heat but also produced gaps along the bondline wherethe “center” of the wound coil was located during activation. Such toolsin combination with the inventive tapes provide more than sufficientheat in the centerline region to melt not only a traditional thicknessof hot melt adhesive but an excess of the adhesive as well. In essence,the centerline benefits from the heat of the two opposing edges of thescored susceptor element as compared to the heat of the single edge atthe outer edge of the susceptor. Thus, the combination of these newcarpet seaming tapes and the traditional induction tools provides a newand useful method of carpet seaming as well as a synergistic carpetseaming system.

The method of use of the tapes and tools of this aspect of the inventionare the same as mentioned above for the tapes having the “dead” zones.Specifically, the tape is placed under the carpet with the centerline ofthe tape corresponding to the seam. The carpet edges are placedtogether, the tool aligned with the seam and activated for a sufficientperiod of time to melt the adhesive. Then, the tool is advanced to thenext activation site and the trailing seam pressed to force the backingof the carpet into the hot melt adhesive. This process is repeated untilthe tape seam is completed.

In a third aspect of the present invention, there is provided animproved induction carpet seaming method wherein tapes of the typedescribed above as well as conventional induction activatable carpetseaming tapes may be used in combination with an induction tool having a“double racetrack” coil for providing carpet seams with strong bondseven at the centerline of the tape. This aspect of the present inventionalso relates to novel tapes and tools specifically designed for use inthe aforementioned method.

As discussed earlier, FIG. 4 shows the footprint of a double racetrackcoil with its opposite current paths 29. For purposes of exaggeratingthe opposing flow, the arrows are shown outside of the coil elements 21,when in fact the flow is within the coil elements of the coil 20.Although the particular embodiment shown is of dual elliptical coilelements 21, the coil elements could just as well be of a differentshape, e.g., circular, square or rectangular; however, shape may affectthe efficacy of the tool, particularly insofar as the shape affects thefunctional length of the coil, and thus tool. In particular, it has beenfound that the geometry of the coils affects the heating characteristicsfor a susceptor of a given width and thickness. The chief variables ofthe coil geometry are the wire type, total length of wire, windingpattern, and separation between the two lobes of the coil, all of whichdetermine the centerline activation width 28 and the overall coil width27 as well as the functional length 25 of the tool. The coil length isselected to balance power transfer, activation cycle time, and desiredseaming rate. For example, a typical 120V AC powered tool can activateabout 1 inch/second of seam tape that is coated with a low melttemperature, hot melt adhesive that is approximately 0.8 mm thick. Acoil having a functional length of 8 inches would require about 8seconds to activate the 8 inches of seam it covers. The cycle time isthen about 10 seconds (allowing 2 seconds to move the tool) giving aseaming rate up to 48 inches per minute—a rate very competitive with hotiron seaming which is assumed to be approximately 3 feet per minute.

The coil separation 22 must also be optimized to maximize the width ofthe heating band or, alternatively, minimize the total coil width whilemaintaining acceptable heating distribution in the heated band, i.e.,the area corresponding to the centerline bond band. The powerdistribution as a function of separation between the coils isillustrated in FIG. 7. For clarity, the coil winding position, relativeto the centerline axis of the tool, is also shown for each designatedseparation of the coils (71, 72, 73, 74). This corresponds to the crosssection of one of the two individual coil elements in FIG. 4 taken alongline 4 a—4 a, with the gap 22 being equal to the specified separationshown in FIG. 7. In FIG. 7, the Power Density axis of the graphcorresponds to the centerline of the coil 23 (of FIG. 4). Combining amirror image of the plot at the power density axis would provide arepresentation of the power density across the full width of thesusceptor.

As seen in FIG. 7, when the coil separation is zero 71, the heatingbandwidth is minimum and the power distribution, and therefore thetemperature, is greatest at the centerline of the coils. At constantpower and energy, we find that as the coil separation is increased theuseful heated zone, i.e., that area corresponding essentially to thecenterline activation width 28, widens and the magnitude of the heatingmaximum located at the centerline falls. This manifestation is shown bythe plots 72, 73 and 74 for coil separations of 10 mm, 20 mm and 30 mm,respectively. Eventually, the separation grows too large such thatheating at the centerline falls to an unacceptably low value, especiallyfor an adhesive of a given type and thickness.

Notwithstanding the foregoing, as discussed below, while coilseparations (also referred to herein as “gaps” or “coil spacing”) of thewidths mentioned above may be preferred for instances where, in use, thetool or coil is properly aligned over the centerline of the tape, suchis not always possible. Consequently, although there is a trade off inthe power density in the centerline region with wider gaps, such widergaps also provide an overall wider activation width, as seen in FIG. 7,so that if misalignment occurs, there is still a sufficiently wide seambond band formed. Of course the gap must not be so great as to result intoo little power and poor heating. In this instance, wider coil elementscombined with wide, but not excessively wide gaps, can accommodate powerneeds together with addressing the activation width.

As a consequence of their experimentation, Applicants have designed aninduction tool that is especially beneficial for carpet seaming and likeseaming applications. As shown in FIG. 4, tools in accordance with thisaspect of the present invention have a coil spacing or gap 22 of between5 and 30 mm, preferably between 10 and 20 mm; a centerline activationwidth 28, i.e., that distance from the inside edge of one coil loop tothe inside edge of the opposing coil loop, of at least about 0.75 inch,preferably at least about 1.0 inch, but generally less than 3 inches,most preferably about 2 inches, and an overall coil width 27 that isless than the width of the susceptor of the tape to be activated andwill most likely be of no more than about six inches, preferably no morethan about four and one-half inches. In following, the element width 26of the coil elements will be from about 0.25 to about 0.75 inch,preferably about 0.5 inch. The functional length 25 of the coil, i.e.,the straight edge portion of the coil, can vary and is more a functionof the economics and power output of the tool as well as the desiredspeed of the seaming process. Generally speaking, the functional lengthis between about 2 to 12 inches, preferably from about 4 to 10 inches.Longer functional lengths, though possible, make the tool costineffective and more difficult to use, particularly from a hand-heldperspective. Shorter functional lengths make the tools difficult to usein that so many more individual advancement and activation steps will berequired to bond a seam of a given length.

Seaming tapes to be used with the foregoing double racetrack coils willhave a susceptor width that is at least the same as, preferably greaterthan the overall coil width 27, preferably from about 1.05 to 2.5 times,more preferably 1.1 to 1.5 times, the width of the coil. Reference hereto susceptor width includes the full width (combined width) of theactive susceptors in the case where a slit susceptor is used, butexcludes those portions of a susceptor that have been isolated to create“dead” zones or that are so narrow as not to be recognized by theinduction tool. Wider susceptors could be used, but, except as notedbelow with respect to addressing concerns of induction toolmisalignment, there is no performance benefit and the costs associatedwith the susceptors make them less desirable. If the susceptor width issmaller than the overall coil width then very strong edge heating occursin the susceptor and edge burning or overheating will occur before or bythe time that the center region is sufficiently heated to form asuitable carpet seam. This overheating results in damage to thesecondary carpet backing, reducing strength, which may lead to carpetseam failure during stretching. Furthermore, there comes a point wherethe susceptor width is so small that the induction tool fails torecognize the susceptor altogether, much as noted above with the “deadzones. Thus, where a slit susceptor is used to activate the adhesive,the individual susceptor elements should be at least about ½, preferablyat least about ⅔, the width of the coil.

FIG. 8 illustrates the calculated results of a series of finite elementanalyses using the analysis program MEGA from the University of Bath, inthe United Kingdom for tapes having susceptors of different widths whenactivated by a double racetrack induction coil having an overall width(denoted by number 27, in FIG. 4) of 78 mm. Plots 81, 82 and 83correspond to susceptor widths of 80 mm, 90 mm and approximately 178 mm,respectively. Plot 81, which illustrates the normalized power densityprofile of a susceptor that is approximately 1.026 times the width ofthe coil, shows a high edge effect heating, nearly twice as much powerdensity is delivered to the edge as to the centerline. Plot 82, whichillustrates the normalized power density profile of a susceptor that isapproximately 1.154 times the width of the coil, shows a relatively evenheating between the centerline and the edge. Such heating characteristicis especially desirable. Finally, Plot 83, which illustrates thenormalized power density profile of a susceptor that is approximately2.24 times the width of the coil, shows good centerline heating withlittle edge effect heating. Such a power density profile is desirable,as noted above, where there is only a desire to bond at the centerlineand/or no adhesive is found in the edge region of the susceptor.Depending upon the thickness and transition temperature of the adhesive,as well as the duration of activation of the tool, it is clear thatsusceptor width can play a major role in the efficacy of a seam.

Generally speaking, as noted above, the desired power densitycharacteristic is where the power density at the centerline isequivalent to or nearly equivalent to the power density at the susceptoredge, especially where the adhesive thickness is relatively constantacross the width of the tape or at least in the centerline and edgeregions. Of course, some variation in the power density is not ofconcern and would be desired if the higher power density corresponded toa thicker region of adhesive. Still, since heat transfer from thesusceptor to the adhesive and, perhaps more importantly, through theadhesive itself, is a limiting factor, there is the opportunity forexcessive heat build up in regions of the susceptor having higher powerdensity. Thus, very high power density is not necessarily desirable asthe heat may not transfer quick enough to avoid scorching in theaffected region. Additionally, since the thickness of the susceptor alsoaffects energy absorption, thus power density buildup, it is alsopossible to vary the thickness of the susceptor in given regions tolessen the disparity in power density. Increasing susceptor thicknesswill decrease power dissipation (at a fixed coil excitation current).This, however, introduces other issues, including cost factors that maymake this a less desirable alternative. In any event, given the sharpincrease in power density at the edge between Plots 81 and 82, it isclear that while susceptors that have a width the same as the coil maybe suitable, widths smaller than the coil will lead to unacceptable edgeheating and failure.

The seaming tapes according to the preferred embodiment of this aspectof the present invention must have adhesive in both the centerlineregion and in the area overlying the edges of the susceptors, unless thesusceptor is much wider, e.g., at least about 1.25, preferably at leastabout 1.5, times wider, than the coil width. This is because theadhesive overlying the edges of the susceptors acts as a heat sink,absorbing heat generated in the edge region. Generally speaking, even ifthe power density in the edge region is not sufficient to causescorching, it is preferable to have the adhesive present at the edgeregion to provide an additional bond site for the tape. It may enhancethe strength or appearance of the seam, e.g., there are some in the artwho believe the creation of a bond of good strength removed from themain bond or seam area will help reduce some of the stresses on theprimary seam and help alleviate peaking.

In a preferred embodiment, there are provided novel inductionactivatable seaming tapes comprising a base layer having a width of atleast four, preferably at least 4.5 inches; a susceptor layer whereinthe activatable susceptor is at least 3 and preferably at least 3.5inches wide, a reinforcing layer, and at least one adhesive layerwherein the adhesive is present in the centerline region and comprisesan adhesive strip or series of closely spaced, parallel beads in aregion that is at least 1.5, preferably about 2 inches wide. Preferably,the tape will have adhesive in the ¼ to ½ inch section of the tapedirectly overlaying the edge of the activate susceptor. In a morepreferred embodiment, the adhesive at the centerline and edges will beof sufficient thickness to allow the adhesive to work into the carpetbacking and seam area. Though seaming tapes of less than four incheswith an aluminum foil layer are commercially available for use in thehot iron seaming method where the foil provides a heat reflectivesurface, such tapes are too narrow to provide a sufficient bond band atthe centerline without overheating the edges of the tapes. Applicantshave found that by using wider tapes, they can create a tool or use atool whose coil width, especially its centerline activation width, issufficient to generate a suitably wide bond band area.

The method of forming the seams in accordance with this third aspect ofthe present invention is the same as set forth above for the otheraspects. Activation times, energy levels, frequency, etc., is all amater of choice and readily ascertainable by those skilled in the art,taking into consideration the factors mentioned in this disclosure. In apreferred aspect of the present invention, the induction tool will be asmart tool, capable of detecting energy consumption or draw by thesusceptor and adjusting the output accordingly to ensure proper heatingwithout over heating.

The foregoing discussion concerning the various aspects and embodimentsof the present invention presumes, for the most part, that the tool isproperly aligned with the centerline of the tape during activation ofthe tape, i.e., that central axis of the induction tool or coil, in thecase of the double racetrack coil, is centered over the centerline ofthe tape. This is important inasmuch as misalignment of the toolrelative to the centerline of the tape will adversely affect the optimalperformance of the activation and, thus, the seam to be formed. To avoidsuch concerns, one may use an apparatus or tool which aligns theinduction tool directly over the seam. Such tools are disclosed in U.S.Provisional Patent Application Ser. No. 60/443,403, filed Jan. 29, 2003,of Green et. al. Additionally, one could adapt alignment tools used forhot iron seaming methods to be used for induction tools as well, seee.g., Anderson, U.S. Pat. No. 4,584,040.

Alternatively, one can modify the widths of the tapes and susceptors toaccount for misalignment. In this respect, for each ¼ inch that the toolis aligned off of the centerline of the tape, the width of the susceptorwill need to be an additional ½ inch wider overall. This is because theheating pattern for a given tool will shift equally with themisalignment, i.e., if the tool is misaligned by ⅓ inch, then theheating pattern is likewise misaligned by the same ⅓ inch. The need toincrease the susceptor width to accommodate misalignment is particularlyimportant, if not critical in the absence of an alignment tool orextreme skill, where the width of the susceptor is less than 1.1 timesthe width of the coil, perhaps even less than 1.2 times the width of thecoil, depending upon the skill of the operator as well as the absolutedimensions of the tool and susceptor. For example, if the tool were of 4inch width and the susceptor 4.8 inches (1.2 times the width of thecoil), a misalignment of ¼ inch may not be an issue whereas a ½ inchmisalignment may. Thus, in commercializing a tape for use with a giventool, one may want to accommodate a predetermined level of misalignment,by incorporating additional width into the susceptor to act as atolerance for the misalignment. Again, by way of illustration, if theoptimum susceptor width for a given tool, assuming exact alignment, is1.1 times the width of the coil, but the likely skill is such thattypically one could expect up to ½ inch misalignment, then the optimumsusceptor width, for commercial purposes, will be 1.1 times the width ofthe coil plus 1 inch. Thus, the ranges of acceptable widths recitedabove for the susceptors would be adjusted accordingly, and suchenhanced width tapes, systems and methods are and are intended to beencompassed by and embraced by the teaching of this patent and itsclaims. In these instances, wider gaps between the coils of the doubleracetrack coil and/or wider coil elements resulting in wider overallactivation widths (28 in FIG. 4) are desirable to help offset concernsof misalignment.

Furthermore, while the foregoing discussion has focused on a properalignment of the axis of the induction tool and coil with the centerlineof the tape, it is also possible to bond and properly activate by havingthe axis of the induction tool perpendicular to the axis of the tape,particularly with tools whose coils are elongated, i.e., the length ofthe coils are considerably larger than their widths. This method ofbonding is especially applicable and desirable for effecting bonding ofthe ends of the tapes. Thus, in one aspect of the seaming methodsdescribed above, the first activation may be one transverse orperpendicular to the tape to form the initial bond at one end of thetape followed by successive activations with the axis of the tool andthe centerline being parallel until the tool reaches the opposite end ofthe tape where, once again, the tool is turn transverse to the tape toeffect the last bond at that end of the tape. When using the inductiontool in the transverse mode, adjustments must be made relative to thepower and energy transfer to the tape to avoid excessive heating at thesusceptor edge.

As another feature of the present invention, those skilled in the artwould readily recognize that the tapes described herein can be modifiedto make the same two-sided for overlap seam bonding and for bonding therolled good to an underlying substrate. In this respect, two tapes maybe bonded back to back or one may build up the tape on both sides of thebase layer.

Furthermore, while the methods described herein speak more often of asequential activation and bonding, the seams of the present inventionmay also be made by a continuous seaming method where the tool iscontinuously or very rapidly activated or fired as the tool is movedalong the seam at a constant rate.

Finally, again, while the invention has been described most prominentlyin terms of carpet seaming, it is clear that the same can be used ormodified for use with any number of rolled goods and the like.Additionally, it is easily seen why the tapes, tools and seaming systemscombining the tape and the tool as taught herein provide numerousbenefits over existing technologies for seaming, particularly carpetseaming. It is also evident that these tapes, tools and systems areespecially beneficial for making repairs to rolled goods, whether at theseam or in the body of the roll goods. For example, should a burn occurin a carpet, the section can easily be excised and replaced with anothersection of carpet. This is so for even very small sections of carpet tobe replaced.

The following examples and comparative examples are provided to furtherillustrate the invention. These examples are not meant to limit thebroad teaching and scope of the invention.

Unless otherwise indicated, the induction tool used in the followingexamples was of the type described in Reiss et. al. (U.S. Pat. No.6,509,555) with the exception that the coil element of the tool wasreplaced with a double racetrack coil (See FIG. 4) wherein each coilelement (21) had a functional length (25) of approximately 8 inches, anelement width (26) of approximately ½ inch, with a coil gap (22) ofapproximately ½ inch and a total width (27) of about 3 inches. Inpreparing the seam, unless otherwise indicated, the axis of the tool(23) was aligned with the centerline of the tape and the tool activateda total of 9 times to deliver the energy specified in each example andto form a bond of approximately 8 inches in length corresponding to theactivation length of the tool.

EXAMPLE 1 3½ Inch Tape with Inactive Areas to Prevent Squeeze Out

Two seaming tapes were prepared as follows. A 3½ inch wide, 0.000285inch thick aluminum foil was laminated to a 3½ inch wide base sheet thatis formed of unbleached, 30# Kraft paper. A 0.007 inch thick layer ofadhesive (RHM494 available from Western Adhesives of Kansas City, Mo.)was applied to the surface of the foil using a heated iron. A 3 incheswide layer of woven cotton and fiberglass mesh was placed on top of theadhesive, centered and bonded to it using a warm iron. Another 0.007inch thick layer of adhesive was applied to and bonded to the topsurface of the fabric mesh using a heated iron. Two layers of ½ inchwide, 0.007 inch thick adhesive strips were applied to the edges of thetape and attached with a warm iron. The two tapes differed only in thaton one tape, prior to the first application of adhesive, a cut was madethrough the aluminum foil, but not through the Kraft paper,approximately ¼ inch from each outer edge of the tape.

A 12 inch long piece of each tape was placed on top of a ½ inch thickcarpet pad made of reclaimed polyurethane foam with the adhesive sidefacing away from the pad. Two pieces of beige Softbac carpet, each about24 inches in length, (available from Shaw Industries) were overlaid onthe tape and configured so that their edges met at the center of thetape.

The induction tool was placed on the top surface of the carpet over thetape having the cut foil and activated 9 times successively to deliver atotal of 3600 J at 300 W. Upon examination of the back of the seam itwas evident that the adhesive had melted and flowed into the backing ofthe carpet up to, but not beyond, the portion of the foil that wasscored. The induction tool was then placed on the top surface of thecarpet over the non-scored tape and activated 7 times successively todeliver a total of 2800 J at 300 W. Upon immediate examination of theback of the bonded seam, it was evident that the adhesive had melted andflowed beyond the width of the tape and bonded it to the carpet pad.

This example demonstrates that scoring or cutting the foil susceptorprevented it from heating and melting the adhesive thus preventingsqueeze-out.

EXAMPLE 2 Slit Tape with Single Pancake Coil

Two seaming tapes similar in construction to FIG. 6 were prepared asfollows. A 3½ inch wide, 0.000285 inch thick aluminum foil was laminatedto a 3½ inch wide base sheet that was formed of unbleached, 40# Kraft. A0.003 inch thick layer of adhesive (HM-075 available from SouthernChemical Formulators, Inc. of Mobile, Ala.) was applied to the aluminumsurface using a heated iron. A 3 inch wide layer of woven cotton andfiberglass mesh was placed on top of the adhesive, centered and bondedto it using a warm iron. Another 0.003 inch thick layer of adhesive wasapplied and bonded to the top surface of the fabric mesh using a heatediron. Two layers of ½ inch wide adhesive strips, 0.003 inch thick, wereapplied to the edges of the tape and attached with a warm iron. The twotapes differed only in that on one tape, prior to the first applicationof adhesive, a cut was made through the aluminum foil, but not throughthe Kraft paper, along the centerline of the tape.

A 12 inch long piece of each tape was placed on top of a ½ inch thickcarpet pad made of reclaimed polyurethane foam with the adhesive sidefacing away from the pad. Two pieces of beige Softbac carpet, each about24 inches in length, (available from Shaw Industries) were overlaid onthe tape and configured so that their edges meet at the center of thetape.

A single pancake type induction coil of Litz wire was wound in anelliptical shape measuring about 9 inches long and 3 inches wide. Thecoil was then attached to an induction tool of the type described inReiss et. al. The device was set to deliver 4000 J at 400 W.

The induction tool was placed on the top surface of the carpet over thescored tape and activated to deliver a total of 4000 J at 400 W. Uponexamination of front and back of the seam it was evident that theadhesive had melted and flowed into the seam and had bonded across thefull width of the tape. The induction tool was then placed on the topsurface of the carpet over the non-scored tape and activated to delivera total of 4000 J at 400 W. Upon immediate examination of the back ofthe bonded seam, it was evident that the adhesive has not melted andflowed in the center of the tape.

This shows that scoring of the susceptor along the centerline allowed atraditional induction coil to sufficiently heat the center of region ofthe tape, thus enabling a strong bond at both the center and edgeregions of the tape.

EXAMPLE 3 3½ Inch Double-sided Tape to Seam Carpet and Bond to Floor

A double-sided tape was prepared by bonding together two single-sidedtapes constructed as follows. A 3½ inch wide, 0.000285 inch thickaluminum foil was laminated to a 3½ inch wide base sheet that is formedof unbleached, 40# Kraft paper. The aluminum foil was then coated with a0.003 inch thick layer of adhesive (HM-075 available from SouthernChemical Formulators, Inc. of Mobile, Ala.). Two layers of ½ inch wide,0.003 inch thick, adhesive strips were applied to the edges of the tapeand two layers of 1 inch wide, 0.003 inch thick adhesive film wereapplied to the center of the tape and attached with a warm iron. Thesingle sided tapes were bonded to one another by applying spray adhesiveto the paper backings and pressing them together to form thedouble-sided tape.

A 30 inch long piece of the double-sided tape was placed on top of a ¼inch thick plywood board. Two pieces of beige Softbac carpet, each about30 inches in length, (available from Shaw Industries) were overlaid onthe tape and configured so that their edges met perpendicular to thecenter of the tape. The above-mentioned tool having a double racetrackinduction coil of ½ inch coil spacing and 8 inches in overall length wasplaced on the top surface of the carpet over the tape and activated todeliver 4500 J at 500 W. Upon immediate examination of the bond, it wasevident that the seam had been made and the carpet was securely bondedto the plywood.

EXAMPLE 4 3½ Inch Double-sided Tape to Seam Textiles

A double-sided tape was prepared as in Example 3. A 12 inches long pieceof the double-sided tape was placed between two 9 inches long clothstrips to form an overlap seam between the pieces of fabric. Theinduction tool was placed over the seam and activated to deliver 2500 Jat 300 W. Upon immediate examination of the bond, it was evident thatthe seam had been made and the fabric pieces were securely bonded to oneanother.

EXAMPLE 5 3½ Inch Single-sided Low Profile Tape to Form Butt Carpet Seam

A 3½ inch wide, 0.000285 inch thick aluminum foil was laminated to a 3½inch wide base sheet that is formed of unbleached, 40# Kraft paper. Thealuminum foil was then coated with a 0.003 inch thick layer of adhesive(HM-075 available from Southern Chemical Formulators, Inc. of Mobile,Ala.). A 3 inches wide layer of woven cotton and fiberglass mesh wasplaced on top of the adhesive, centered and bonded to it using a warmiron. Another 0.003 inch thick layer of HM-075 was applied to and bondedto the top surface of the fabric mesh. Two layers of ½ inch wide, 0.003inch thick adhesive strips, were applied to the edges of the tape andtwo layers of 1 inch wide, 0.003 inch thick, adhesive film were appliedto the center of the tape and attached with a warm iron.

A 12 inch long piece of this tape was placed on top of a ½ inch thickcarpet pad made of reclaimed polyurethane foam with the adhesive sidefacing away from the pad (toward the carpet backing). Two pieces ofbeige Softbac carpet, each about 24 inches in length, (available fromShaw Industries) were overlaid on the tape and configured so that theiredges met at the center of the tape. The induction tool was placed onthe top surface of the carpet over the tape and activated to deliver4000 J at 400 W (10 second activation). Upon immediate examination ofthe bond, it was evident that the adhesive had melted and flowed intothe backing of the carpet.

This procedure was repeated again on a larger piece of carpet and theinduction tool was used to activate the adhesive tape ahead of thecarpet installer. The installer activated the tape, slid the toolapproximately 7 inch to the next location, activated it again, and whilewaiting for the subsequent activation, briefly inspected the carpet toensure the desired seam was produced and found that the work necessaryto create the desired seam was less time-consuming than with the hotiron method. This procedure was very similar to the procedure used todaywith the added benefits described above. After the seam was complete,the adhesive was allowed to cool without examination of the bond. Thecarpet was stretched with a power stretcher and placed on tack stripsdesigned to secure carpet to flooring. The seam remained intactthroughout the operation and upon visual examination, appeared to be ofhigher quality than one produced adjacent to it using the traditionalhot iron method.

EXAMPLE 6 3½ Inch Single-sided Tape with Excess Adhesive at Edges andCenter

A tape was prepared in accordance with Example 5 following which a beadof adhesive (HM-049 available from Southern Chemical Formulators, Inc.of Mobile, Ala.) inch diameter was affixed to the center of the tapeusing an aerosol adhesive.

A 12 inch long piece of this tape was placed on top of a ½ inch thickcarpet pad made of reclaimed polyurethane foam with the adhesive sidefacing away from the pad. Two pieces of beige Softbac carpet, each about24 inches in length, (available from Shaw Industries) were overlaid onthe tape and configured so that their edges met at the center of thetape. The induction tool was placed on the top surface of the carpetover the tape and activated to deliver 4000 J at 400 W. Upon immediateexamination of the bond, it was evident that the central bead ofadhesive had melted and flowed onto the edges of the carpet backing.

EXAMPLE 7 Conventional Hot Iron Tapes v. Induction Tape

In this example three commercially available 3.75 inch wide hot ironseaming tapes, each having an aluminum foil layer incorporated into andextending the full width of the backing to reflect heat passing throughthe hot melt from the iron and thus, presumably, enhancing melt of thehot melt adhesive, and an adhesive layer that provided an adhesive freeedge of about ½ wide along each edge of the tape, a 1.9375 inch wideelectrically activated seaming tape having a 0.002 inch conductive foillayer for resistive heating and a 4.5 inch wide induction activatableseaming tape made in accordance with the teaching of the presentinvention were evaluated to assess their activation by induction. Thethree commercial tapes were Bond Loc 90LTG, Roberts GT330 and SeamMaster Gold.

A 12 inch long piece of each tape was placed on top of a ½ inch thickcarpet pad made of reclaimed polyurethane foam with the adhesive sidefacing away from the pad (toward the carpet backing). Two pieces ofbeige Softbac carpet, each about 12 inches in length, (available fromShaw Industries) were overlaid on the tape and configured so that theiredges met at the center of each tape. In these series of experiments,the double racetrack induction tool had a coil separation or gap ofabout ⅝ inch and a total coil width of about 3⅝ inches. The inductiontool was placed on the top surface of the carpet over the tape andactivated to deliver 3500 J at 600 W.

Examination of the seams formed with the three commercial hot iron tapesshowed visible signs of paper charring and damage to the carpet,evidence of overheating in the edge region of the reflective foil.Without adhesive overlying the edges of the reflective foil, there is noheat sink, other than the paper backing and carpet, to absorb the heatgenerated in the foil edge. The centerline area of the tape showed poorand intermittent melting of adhesive, indicative of an incomplete seamwith little or poor strength. Because of the limited width and thicknessof the conductive element of the resistance tape, the induction toolfailed to recognize the tape and did not deliver any energy to the tape.On the other hand, the tapes made in accordance with the teaching of thepresent invention showed no signs of charring or overheating butexcellent activation, thus melting of adhesive, in the centerline regionof the tape.

It should be understood that the foregoing description is onlyillustrative of the invention. Various alternatives and modificationscan be devised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances falling within the scopeof the appended claims.

1. An improved induction seaming method for activating an inductionactivatable seaming tape having a susceptor with an induction tool saidmethod involving the step of activating the seaming tape along the seamwith the induction tool wherein the improvement comprises the step ofturning the induction tool transverse to the tape at one or both ends ofeach seam to be formed and then activating the induction tool for asufficient time to activate the adhesive in order to better activate theends of the seaming tape.
 2. The induction seaming method of claim 1wherein the induction tool has a coil element whose length is longerthan the width of the susceptor and whose width is narrower than thesusceptor.
 3. The method of claim 1 wherein the seam is to be formed ina substrate selected from the group consisting of carpeting, fabric,felt wall covering, and textiles.
 4. A method of producing a seam in asubstrate or between two or more substrates using induction which methodcomprises the steps of: placing an induction activatable seaming tape atthe point where the seam is to be formed, said seaming tape comprising abase layer, a susceptor overlying all or a substantial portion of thebase layer and capable of generating heat upon exposure toelectromagnetic energy, and a heat activatable adhesive layer in heattransfer relationship with said susceptor and overlying all or asubstantial portion of said susceptor layer, but in any event overlyinga centerline of the seaming tape, the centerline of the seaming taperunning the length of the tape; said adhesive layer in contact with thesubstrate, placing an induction tool having a double racetrack inductioncoil, wherein the induction coils are in a side-by-side relationship,over the point where the seam is to be formed whereby the axis of theinduction tool which is defined as the centerline running between andalong the length of each portion of the double racetrack coil isparallel to and substantially centered over the centerline of the tape;activatiug the induction coil for sufficient time to generate sufficientheat in the susceptor to heat the adhesive above that temperature neededto activate the adhesive; and allowing the adhesive to cool therebybonding the seaming tape to the substrate or substrates wherein saidmethod further comprises the steps of turning the induction tool at oneor both ends of each seam to be formed such that the axis of the tool istransverse to the centerline of the seaming tape and then activating theinduction tool for a sufficient period of time to activate the adhesive.5. The method of claim 4 wherein the substrate is a rolled good.
 6. Themethod of claim 4 wherein the substrate is selected from the groupconsisting of carpeting, fabric, felt, wall covering, and textiles. 7.The method of claim 4 wherein the length of the seam is longer than thelength of the induction tool and the method further comprises the stepof advancing the induction tool along the length of the seam to beformed in a continuous or a step-wise process.
 8. The method of claim 7wherein the advancement of the induction tool occurs in a step-wisefashion and the induction tool is activated following each advance oftime tool along the seam.
 9. The method of claim 7 wherein theadvancement is continuous and the induction tool is rapidly andrepeatedly activated as the tool is advanced along the seam.
 10. Themethod of claim 4 wherein the double racetrack coil is of the pancakestyle having elliptical coil elements.
 11. The method of claim 10wherein the double racetrack induction coil has a coil spacing of fromabout 5 to 30 mm and coils loop elements of about 0.25 inch to about0.75 inch wide and wherein the susceptor is from about 1.05 to about 2.5times the overall width of the coil.
 12. The method of claim 4 whereinthe heat activatable adhesive is a hot melt adhesive or a reactive hotmelt adhesive.
 13. The method of claim 4 wherein the seaming tape is adouble sided seaming tape comprising a base layer, two susceptors, eachoverlying all or a substantial portion of the opposing sides of the baselayer and two adhesive layers, each in a heat transfer relationship witheach susceptor layer, at least one adhesive layer being in contact withthe substrate.
 14. The method of claim 4 wherein the induction tool is ahandheld tool.
 15. The method of claim 4 wherein the thickness of theadhesive is greater at the centerline of the seaming tape.
 16. Animproved method of producing a seam in a substrate or between two ormore substrates using induction which method comprises the steps of:placing an induction activatable seaming tape at the point where theseam is to be formed, said seaming tape comprising a base layer, atleast one susceptor overlying all or a substantial portion of the baselayer and capable of generating heat upon exposure to electromagneticenergy, and a heat activatable adhesive layer in heat transferrelationship with said susceptor and overlying all or a substantialportion of said susceptor layer, but in any event overlying a centerlineof the seaming tape, the centerline of the seaming tape running thelength of the tape; said adhesive layer in contact with the substrate,placing an induction tool over the point where the seam is to be formedwhereby the axis of the induction tool is parallel to and substantiallycentered over the centerline of the tape; activating the induction coilfor sufficient time to generate sufficient heat in the susceptor to heatthe adhesive above that temperature needed to activate the adhesive; andallowing the adhesive to cool thereby bonding the seaming tape to thesubstrate or substrates; wherein the improvement lies in the use of aseaming tape whose susceptor has a gap that runs the length of thecenterline of the seaming tape thereby separating the susceptor into twoindividual susceptor elements.
 17. The method of claim 16 furthercomprising the step of turning the induction tool such that its axis istransverse to the centerline of the seaming tape at the ends of eachseam to be formed and then activating the induction tool fir asufficient time to activate the adhesive.
 18. The method of claim 16wherein the seam is to be formed in a substrate selected from the groupconsisting of carpeting, fabric, felt, wall covering, and textiles. 19.An improved method of producing a seam in a substrate or between two ormore substrates using induction which method comprises the steps of:placing an induction activatable seaming tape at the point where theseam is to be formed, said seaming tape comprising a base layer, atleast one susceptor overlying all or a substantial portion of the baselayer and capable of generating heat upon exposure to electromagneticenergy, and a heat activatabloe adhesive layer in heat transferrelationship with said susceptor and overlying all or a substantialportion of said susceptor layer, but in any event overlying a centerlineof the seaming tape, the centerline of the seaming tape running thelength of the tape; said adhesive layer in contact with the substrate,placing an induction tool over the point where the seam is to be formedwhereby the axis of the induction tool is parallel to and substantiallycentered over the centerline of the tape; activating the induction coilfor sufficient time to generate sufficient heat in the susceptor to heatthe adhesive above that temperature needed to activate the adhesive; andallowing the adhesive to cool thereby bonding the seaming tape to thesubstrate or substrates; wherein the improvement lies in the use of aseaming tape whose susceptor extends in both directions from thecenterline of the tape to an edge that is from ½ to ¼ inch from the edgeof the base layer which seaming tape further comprises edge strips of adamming material, said edge strips overlying the whole or a portion ofthe base layer in the two regions between the edges of the tape and theedges of the susceptor.
 20. The method of claim 19 further comprisingthe step of turning the induction tool such that its axis is transverseto the centerline of the seaming tape at the ends of each seam to beformed and then activating the induction tool for a sufficient period oftime to activate the adhesive.
 21. The method of claim 19 wherein theseam is to be formed in a substrate selected from the group consistingof carpeting, fabric, felt, wall covering, and textiles.
 22. A method ofproducing a seam in a substrate or between two or more substrates usinginduction which method comprises the steps of: placing an inductionactivatable double sided seaming tape at the point where the seam is tobe formed, said double sided seaming tape comprising a base layer, twosusceptors, each overlying all or a substantial portion of the opposingsides of the base layer and capable of generating heat upon exposure toelectromagnetic energy, and two heat activatable adhesive layers, eachin a heat transfer relationship with one, but not the same, susceptorlayer and overlying all or a substantial portion of said susceptorlayer, but in any event overlying a centerline of the seaming tape, thecenterline of the seaming tape running the length of the tape; at leastone of said adhesive layers in contact with the substrate, placing aninduction tool having a double racetrack induction coil, wherein theinduction coils are in a side-by-side relationship, over the point wherethe seam is to be formed whereby the axis of the induction tool which isdefined as the centerline running between and along the length of eachportion of the double racetrack coil is parallel to and substantiallycentered over the centerline of the tape; activating the induction coilfor sufficient time to generate sufficient heat in the susceptor to heatthe adhesive above that temperature needed to activate the adhesive; andallowing the adhesive to cool thereby bonding the seaming tape to thesubstrate or substrates.